1. Field of the Invention
The present invention relates to improvements in a heat pump type air conditioner applied to an automotive vehicle.
2. Description of the Prior Art
It is well known that a heat pump type air conditioner is applied to an automotive vehicle and provided with a four-way valve for changing refrigerant flow in a heating operation and a cooling operation. During the heating operation, an outer heat exchanger is used as a heat absorber and an inner heat exchanger is used as a heat radiator. On the other hand, during the cooling drive, the outer heat exchanger is used as a heat radiator and the inner heat exchanger is used as a heat absorber. Such a heat pump type air conditioner is disclosed, for example, in Japanese Patent Provisional Publication No.2-290475 and Japanese Utility Model Provisional Publication No.2-130808.
As shown in FIG. 12, during a heating operation, a four-way valve 2 is set as indicated by a continuous line in FIG. 12 and refrigerant is circulated as follows: A compressor 1.fwdarw.the four-way valve 2.fwdarw.a first inner heat exchanger 3.fwdarw.a heating heat exchanger 4.fwdarw.a second inner heat exchanger 5.fwdarw.an expansion valve 6.fwdarw.an outer heat exchanger 7.fwdarw.the four-way valve 2.fwdarw.a receiver 8.fwdarw.the compressor 1. Accordingly, the heat of the refrigerant is transmitted to air led by a blower fan 9 and used for heating a passenger compartment. The heat from an engine 10 is transmitted to the refrigerant through the heating heat exchanger 4 and further transmitted from the refrigerant to air forced by a blower fan 11 for heating the passenger compartment. The heat of the air blown by a fan 12 is transmitted to the refrigerant through the outer heat exchanger 7.
On the other hand, during the cooling operation, the four-way valve 2 is set as indicated by a broken line in FIG. 12 and refrigerant is circulated as follows: The compressor 1.fwdarw.the outer heat exchanger 7.fwdarw.tile expansion valve 6.fwdarw.the second inner heat exchanger 5.fwdarw.the first inner heat exchanger 3.fwdarw.the four-way valve 2.fwdarw.the receiver 8.fwdarw.the compressor 1. Accordingly, the heat of the refrigerant discharged from the compressor 1 is radiated into the atmosphere by the outer heat exchanger 7, the heat of air forced by the blower fans 9 and 11 is radiated into the refrigerant by the first and second inner heat exchanger 3 and 5, and the cooled air is supplied to the passenger compartment.
With such a conventional air conditioner, the absorbed heat amount by the outer heat exchanger 7 is decreased during the heating operation under a condition such that the ambient temperature is low, the automotive vehicle is running, or it is raining or snowing. Furthermore, if the workload of the compressor 1 is constant, the radiated heat amount from the first and second inner heat exchangers 3 and 5, which is the sum of the heat absorbing amount from the outer heat exchanger 7 and the workload of the compressor 1, is decreased, and the heating capacity of the air conditioner is lowered. Additionally, the lowering of the heating capacity invites frost on the heat exchanger. This increases a defrost operation and prevents a stable heating operation. Furthermore, since the conventional air conditioner is arranged such that the flow direction of the refrigerant is changed under the cooling and heating operations, it is necessary to change the design of the conduits of the outer and inner heat exchangers 7, 3 and 5 so as to be durable to high temperature and high pressure.
Also, since the conventional air conditioner is arranged to generate heated air for heating by utilizing the waste heat of the engine 10 during the heating operation, this air conditioner can not sufficiently operate if applied to a vehicle which only has a small heat source, such as to a solar car or electric vehicle.
Furthermore, since the conventional air conditioner is arranged to select one of the cooling and heating operations on the basis of the difference between a target outlet air temperature and an inlet air temperature to the inner heat exchangers 3 and 5, and can not simultaneously carry out both cooling and heating operations, a dehumidifying heating operation can not be implemented by the conventional air conditioner.
Additionally, it is necessary to exactly implement the dehumidifying heating operation so as not to cause the clouding or fogging of windows which is generated in connection with the relationship between the ambient air and the compartment air